1. Field of the Invention
The present invention relates to image forming apparatus such as electrophotographic copying machines and laser beam printers, and more particularly to a control system for an image forming apparatus having a plurality of developing units, cassettes or other means.
2. Description of the Prior Art
Recently, image forming apparatus such as electrophotographic copying machines, laser beam printers and the like have been proposed wherein a plurality of paper feed cassettes are provided for accommodating copy paper of different sizes, a plurality of developing units are arranged around the surface of an electrostatic latent image bearing member in the direction of movement of the member, or copying operation can be conducted under a plurality of copy modes.
Further image forming apparatus generally have the automatic reset function of resetting all the copy modes to the initial standard state unless an input is given from the operation panel within a predetermined period of time after the completion of an image forming operation. The term "auto-reset" as used herein means the above-mentioned automatic reset function.
On the other hand, image forming apparatus have been proposed wherein a device or copy mode other than the device or mode currently in use for image forming operation can be specified by an advance input during the image forming operation. However, in the case where the next user fails to promptly make preparations and initiate the subsequent image forming operation, the auto-reset function is performed before the subsequent operation even if he entered copying conditions, different from the current conditions, in advance during the current image forming operation. Consequently, the advance input becomes useless.
This problem is encountered, for example, with apparatus wherein one of a plurality of developing units is selectively operated for development. Unexamined Japanese Patent Publication SHO No. 60-232566 discloses such an apparatus which is adapted to accept an advance input specifying a particular developing unit during the current image forming operation and to effect a change-over from the developing unit in use to the specified one immediately after the completion of the current operation. The disclosed apparatus has the advantage that the time required for using the developing unit, different from the one currently used, for the next image forming operation can be reduced only to the time required for the change-over, thereby improving the work efficiency.
Nevertheless, if the auto-reset means functions before the next user starts the next image forming operation despite the advance input, there arises the problem that the above-mentioned advantage can not be utilized.